Max 6 and C++ – crash

I’ve been looking at Graham Wakefield’s Max C++ implementation, and I’m having a problem with the msp example object.
It compiles just fine, loads into Max, I can patch up the inlets and outlets as well – but after that, Max crashes whenever I try to modify the patch.
From the crash log, I’ve worked out Max crashes during msp32wrapper_perform64 (from com.cycling74.MaxAudioAPI).

I haven’t modified the example’s code, though I had to update the project’s settings in Xcode (from MacOS 10.4 to 10.6, as well as the compiler)